The Alexandra Palace TV Station

When the BBC began telecasting in 1936, Alexandra Palace, on a hill
in London, was chosen as the site for the transmitter and studios.
This was the only TV station in England until a second station was
started in Birmingham in 1950. Here are program schedules from the early days of Alexandria Palace and a British Pathe film segment.

When England declared war on Germany in 1939, the transmitter was converted to send out signals to confuse German navigation signals for their bombers. Here is a video from the Alexandra Palace Television Society explaining the history and technology (5 parts), and an article in 405 Alive describing the use of the system.